June 22, 2010 -- The higher a man's level of natural testosterone, the higher his risk of heart problems, according to a new study that looked at testosterone and heart disease only in men 65 and older.

"Increasing levels of testosterone were associated with a higher risk of heart disease and death from heart disease," says Kristen T. Sueoka, MD, a resident physician in internal medicine at the University of California San Francisco, who presented the findings at ENDO 2010, the annual meeting of The Endocrine Society, in San Diego.

Research on testosterone and heart disease has yielded conflicting findings, she tells WebMD, prompting her to do the study.

Sueoka and her colleagues focused on 697 men, average age 72, who were seen at six different U.S. centers from 2000 to 2005 while participating in a study to evaluate fracture risk in older men.

None was taking hormone supplements.

During an average of nearly four years of follow-up, 100 men (14%) had a coronary heart disease event such as a heart attack.

When Sueoka looked at the testosterone levels from the blood tests, she found that higher total testosterone was associated with an increased risk of coronary heart disease.

The men were divided into four groups, from lowest testosterone levels to highest. "People in the two highest quartiles had a 2.2 times increased risk of heart disease compared to those in the lowest."

Defining low vs. high is complicated, Sueoka says, as there is controversy about the measurements. She categorized the men as low vs. high using only the measurements of the 697 men, so the low and high categories are relative.

Higher testosterone, she says, appears to be linked to a higher risk of heart disease once men pass age 65.

Her study was supported by the National Institute on Aging, National Heart Lung and Blood Institute and National Institute of Arthritis and Musculoskeletal and Skin Diseases.

Debate on Testosterone and Heart Health

Research findings have gone back and forth about testosterone and heart health, Sueoka tells WebMD. "There are some cross-sectional studies [snapshot in time studies] that have shown an association between low testosterone and higher risk of heart disease death."

"Experts seem to agree that low testosterone is associated with a higher risk of death from heart disease," she says. But it's difficult to know which came first, she says, as men may first get sick and then testosterone declines.

Still under debate, she says, is whether or not testosterone has a cause-and-effect role in heart health.

Exactly how high testosterone might be linked with coronary heart disease isn't clear, Sueoka says. "In some animal models and in the lab, if you give testosterone it can lead to atherosclerosis," she says. But, she adds, there is also some evidence to the contrary, that it improves blood flow and dilates blood vessels, improving heart health.

He points, for instance, to the large EPIC-Norfolk study from Europe, in which the testosterone-heart disease link was studied in more than 11,000 men. Researchers concluded that low testosterone may be a marker for those at high risk of cardiovascular disease.

"These findings in older men come a bit of a surprise," he tells WebMD. He says the number of participants, under 700, is quite small compared to the European study.

"I think it's fair to say we still don't know a clear-cut answer to the question, 'Does testosterone contribute to or protect from cardiovascular disease?'" Shah says. "I am not fully convinced that this study answers the question of whether high testosterone is protective or detrimental for heart disease."

Until more research is in, he says, "If men have testosterone deficiency, replacing that is probably quite reasonable to preserve muscle mass and improve libido."

More research is needed, agrees Sueoka, who says she can't comment on testosterone supplementation, as her study looked only at natural testosterone levels.

If future studies confirm the link she found between high testosterone and heart disease, she says, "the second question has to be, 'If you give [supplemental] testosterone, are you causing more heart disease?'"

This study was presented at a medical conference. The findings should be considered preliminary as they have not yet undergone the "peer review" process, in which outside experts scrutinize the data prior to publication in a medical journal.

SOURCES: Kristen T. Sueoka, MD, resident physician in internal medicine, University of California, San Francisco School of Medicine.